Feature/previous window 1.6.1

Re-created from #132 to change the base branch and to get the better diffs.

Two notes:
* This pull request contains a change to README.md since this branch was once merged with develop. It should be ok, as long as you'll merge to develop sometime in future.
* This pull request will conflict with #142 (fix XIB regressions.) I recommend taking #142 first, and I'll update this pull request. I wished to create a pull request that you could merge both at once, but it looks like I can't set base branch to my own, so this looks like the only way to go.

Other than that, the patch looks clean (i.e., contains my changes only.)